Semiconductor chips are usually mounted to form semiconductor components for protection against external influences, for mechanical stabilization and for connection to an external circuit. So-called FBGA semiconductor components are known in this case. In this case, “FBGA” stands for “Fine Ball Grid Array,” which means that small solder balls are arranged in gridlike fashion in an array on a solder ball side of a substrate.
The small solder balls are fixed on ball pads. The ball pads are part of a conductor structure that serves for the electrically conductive connection to bonding pads. The conductor structure with its ball pads and the bonding pads is usually likewise arranged on the solder ball side of the substrate. The semiconductor chip or a stack of semiconductor chips is or are situated on the chip side of the substrate opposite to the solder ball side. In this case, the semiconductor chip (the bottommost semiconductor chip in the case of stacks of semiconductor chips) is placed by its patterned side onto the chip side of the substrate and fixed there. For the electrically conductive connection between the semiconductor chip and the bonding pads, on the one hand bonding pads are likewise provided on the semiconductor chip, these bonding pads quite generally being arranged in the center of the semiconductor chip. Situated precisely in this region there is an opening in the substrate, this opening being called a bonding channel. The opening generally has a rectangular form in plan view. Short wire bridges are then drawn from the bonding pads on the semiconductor chip to the bonding pads of the conductor structure and are each fixedly bonded to the bonding pads.
For mechanical stabilization, it is then provided that the semiconductor chip or the semiconductor chip stack is provided with a first housing part and the bonding channel is provided with a second housing part. These housing parts are produced by placing onto the substrate potting tools that have the negative mold of the housing parts to be formed. A potting composition is pressed into these negative molds and then cures. After removal of the potting molds, the housing parts have thus been produced.
The bonding channel has side areas extending between the solder ball side and the chip side. The side areas are usually configured such that they are relatively smooth. It is thus only possible for the potting composition of the second housing part in the bonding channel to form a materially cohesive connection.
This materially cohesive connection has proved to be disadvantageous to the effect that fractures very often occur in this housing part. These housing fractures lead to fractures or tears of the bonding wires in each case in the region of the housing fracture. The consequence of this is that the semiconductor components have an excessively low reliability and thus do not meet the quality requirements.
One possibility for mechanical stabilization of the housing is afforded by reinforcing the housing, either by increasing the thickness or increasing the width. Increasing the thickness is limited by the fact that the solder balls have a small diameter and the height of the housing part must be less than the size of the solder ball diameters. Limits are imposed on the width of the bonding channels since these will have to be made even smaller in view of the object of further miniaturization in the future.
The problem of housing fracture and low reliability has been combated hitherto by searching for suitable materials, which has led to the expensive development of new materials for minimizing stress. This demand for the use of “universal” materials, that is to say those that can be utilized for entire technology platforms, exhibits a very high expenditure in terms of costs and time.
Another possibility has been sought in changing the housing construction, e.g., in the size and thickness of the adhesive between the semiconductor chip and the substrate or changing the chip and substrate thickness.